1. Field of the Invention
The present invention relates to a laser processing apparatus, a laser processing method that can be carried out by using the laser processing apparatus, a method of manufacturing a wiring substrate by the laser processing method, a method of manufacturing a display apparatus including the wiring substrate and a wiring substrate obtained by the laser processing method.
2. Description of the Related Art
Structures produced on the assumption of mass-production have predetermined structure patterns determined in response to purposes. Such a structure may be a wiring substrate including members (wires, etc.) and devices (capacitors, etc.) or a photomask. Also, a structure including a wiring substrate and which uses a photomask in the manufacturing process may be a display apparatus such as a flat display panel display (FPD).
However, predetermined patterns may be incompletely formed on these structures in the manufacturing process and it is frequently observed that members and devices are formed excessively (for example, extended to the outside of a predetermined area) or formed insufficiently (for example, not formed uniformly within the predetermined area).
A specific example will be described using a display apparatus.
A display apparatus (for example, flat panel display) has a picture screen formed of a large number of pixels arrayed in a two-dimensional matrix (XY-matrix) and it has excellent characteristics such as thin, light-weight and low power consumption. Such display apparatuses are classified based on driving systems. An active matrix display apparatus in which a switching element is electrically connected to each pixel electrode can suppress crosstalk occurred between adjacent pixels and therefore has, particularly, excellent image quality (image). For this reason, active matrix display apparatuses have been studied and developed and are widely used as display apparatuses for a personal computer (PC), a television receiver (TV) and other electronic apparatuses. It should be noted that flat panel displays are classified into a liquid crystal display, an organic EL (electroluminescence) display and so on depending on light-emitting systems.
An active matrix display apparatus includes a transparent insulated substrate such as made of glass on which is formed a wiring substrate (or matrix array substrate or array substrate) constructed by stacking lower-layer metal wiring patterns (for example, a plurality of scanning lines), insulating films and upper-layer metal wiring patterns (for example, a plurality of signal lines).
The lower-layer metal wiring patterns and the upper-layer metal wiring patterns extend in the directions perpendicular to each other, are arranged in the form of a lattice. The position corresponding to each cell (intersection) of the lattice may serve as a pixel. The upper-layer metal wiring pattern is connected to a pixel electrode made of a transparent conductive material such as ITO (Indium-Tin-Oxide). Also, each pixel is provided with a switching element that can control the electrode. In the case where this switching element is a thin film transistor (TFT), the gate electrode is electrically connected to the scanning line, the drain electrode is electrically connected to the signal line and the source electrode is electrically connected to the pixel electrode.
Local failure such as defect of an insulating film and disconnection of metal wiring may frequently occur in such wiring substrate. An interlayer short-circuit may be a specific example of local failure. In the interlayer short-circuit, the upper-layer wiring and the lower-layer wiring are caused to electrically connect at the position at which the upper-layer wiring pattern and the lower-layer wiring pattern intersect each other or overlap with each other due to defects of the insulating film and mixing of a non-insulating foreign matter.
If the above local failure occurs in the wiring substrate, then a part of pixels becomes a pixel that stops lighting or a plurality of pixels become a line of pixels that stop lighting in the display apparatus, for example, so that the performance of such image display deteriorates considerably. For this reason, while control of manufacture processes is attempted (reduction of foreign matter, suppression of defect, etc.) to suppress occurrence of such local failure, it is difficult to completely prevent the occurrence of local failures.
Japanese Unexamined Patent Application Publication No. 2001-77198 discloses a method of correcting an interlayer short-circuit at the position in which an upper-layer wiring pattern and an lower-layer wiring pattern intersect each other or overlap with each other. This method is used to correct the interlayer short-circuit at the position in which the upper-layer wiring pattern and the lower-layer wiring pattern intersect each other or overlap with each other. However, since it has been difficult to carry out laser cutting only on the upper-layer wiring pattern in the interlayer short-circuit portion, the interlayer short-circuit is corrected by laser cutting and a bypass wiring process in other areas than the intersecting portion, so that the process is complicated.
Also, Japanese Unexamined Patent Application Publication No. H11-282010 discloses a method that corrects short-circuit between upper-layer wiring patterns. This method is able to correct short-circuit between the upper wiring patterns. However, when the area that should be cut by laser exists also in the lower wiring portion, occurrence of an interlayer short-circuit caused between the upper layer and the lower layer may not always be prevented, because the lower layer also should be cut by laser. As a result, influence of the interlayer short-circuit portion should be removed by cutting other areas with laser and the process is complicated.
As described above, the correcting methods according to related-art are complicated in process and have other disadvantages such as long manufacture throughput.
Also, in the related-art correcting methods, a film thickness of a multilayer film in the wiring substrate has been determined to obtain a small-sized apparatus from the viewpoints of miniaturization and thin apparatuses. On the other hand, the inventors of the present application have found out that laser processing may be optimized only within a range in which correction is determined by a film thickness, if correction is carried out based on an established film thickness. Specifically, the inventors of the present application have found out that a wavelength of laser light or the like should be selected to carry out optimum laser processing without restrictions of the established film thickness.